Calibrating tool



CALIBRATING TOOL Filed Jun 2, 1944 2 Sheets-Sheet 1 50 3 L 52 23 f6 35 Y 4.5 49 57 62 22 35 I 39 4 6 r 28 24 v 21 77 O O 7 O '79 I I v 29 75 31 25 3 if 75 76 67 a5 a3 33 WITNESSES: INVENTOR V w Nz'a/s Mars.

ATTORNEY Patented Dec. 11, 1945 CALIBRATING TOOL Nick Mars, Sharon, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application June 2, 1944, Serial No. 538,352

4 Claims.

My invention relates to a calibrating tool for measuring the pressure developed by a pressuredeveloping device or tool for applying an increasing force to a predetermined value on,a Workpiece operated by the pressure-developing tool being calibrated. My invention is applicable to calibrating the setting of a strap-stretching device of the character in which an increasing force is applied by the device until the force is increased to a predetermined value, at which value the strap-stretching device is automatically locked against further operation to prevent further increase in the tension applied to the strap being stretched.

In the strap-stretching device to be calibrated, a hand-operated strap-stretching tool is employed for stretching or tightening steel straps or bands about a substantially solid mass of material, such as the core structures of electrical transformers, where it is desirable to maintain a predetermined constant tension on the band about the cor parts. The strapstretching device causes force to be applied to the two ends of the strap that is placed about the core, and as the tool is operated, the tension of the strap is increased to a predetermined value, at which value a locking mechanism on the strap-stretching device is released for locking this device against further operation, thus holding the strap under a predetermined tension until it is fastened in its desired position at the desired tension. In order to calibrate the strap-stretching device so that the locking mechanism. thereof will be released at the desired predetermined tension on the steel strap or metal band being stretched, the calibrating tool of the present invention is employed.

It is an object of the invention to provide a calibrating tool that is adapted for measuring the pressure applied by a pressure-developing device or tool having tworelatively movable heads that ar mounted to move toward or from each other, and are arranged to apply a pressure to the workpiece when forced in a direction away from each other.

It is a further object of the invention to provide a calibrating tool for calibrating the setting of a strap-stretching device that is adaptable for employment for stretching a, metal strap about an article, and is provided with means for locking the strap-stretching tool against further operation upon the application of a predetermined force upon the strap being stretched.

Other objects and advantages of my invention will be apparent from the following description of a preferred embodiment of the invention, reference being had to the accompanying drawings, in which:

Figure 1 is an elevational view of a core loop with a strap-stretching device applied for stretching a steel strap about the core of the loop;

Fig. 2 is a detail of a portion of the strapstretching device, shown enlarged and partly in section;

Fig. 3 is an elevational view of the strapstretching device shown in Fig. 1, together with the calibrating tool of the present invention, shown in position for effecting a calibrating operation;

Fig. 4 is a sectional view of the calibrating tool;

Figs. 5a through 5d are views showing the principal parts of the calibrating tool in unassembled relation; and

Fig. 6 is a clamp for releasing the calibrating tool from engagement with the strap-stretching tool upon completion of a calibrating operation.

The invention relates to a portable calibrating tool for calibrating a banding tool or strapstretching device used to apply a predetermined tension to a metal band or steel strap placed about an article. In order to better understand the purpose of the calibrating tool, a brief description of the banding tool or strap-stretching device to be calibrated will first be given.

Referring to the drawings, and particularly to Figure 1 thereof, a strap-stretching tool 5 is shown in position for applying a strap to a core loop 2 comprising two U-shaped portions 3 and 4 having butt joints between them along the adjoining surfaces 5. The tool is used to apply the metal strap 6 about the core loop 2 under a predetermined tension, so as to maintain continuous pressure between the two U-shaped portions 3 and 4 at the butt-joint surfaces 5. As shown, one end I of the strap 6 extends over the corner of the core and along the surface of the core loop passing under a fastening clip or sleeve 8, and is bent at 9 to turn through the clip or sleeve 8 which surrounds the strap, the strap continuing over the end portion 1 of the strap 6 and passing about the core loop and again passing through the sleeve 8 at It], the end i I being positioned so as to be gripped by the tool I for tightenin it about the core loop.

After the strap has been pulled tightly about the core loop by the tool I, the clip 8 which is in the form of a sleeve or. band of metal about the two ends of the strap 6 is crimped or deformed sufiiciently so that the edges of the clip and of the two ends of th strap passing through the the head 2!.

clip are bent to prevent the strap from loosening.

The tool I comprises two relatively movable heads 2I and 22, the head 22 being mounted on a rack bar 23 provided with a rack 24 on its upper side that is engaged by the teeth of a pinion (not shown) within the head 2I that is operated by the lever 25 through a manually-operated lever 26 having a handle 21.

The head 22 is provided with a nose consisting of jaws 28 and 29 which are positioned on opposite sides of the strap end II and, as shown in Fig, 1, press against one end of the clip 8 when the .tool I is in position for tightening the strap H about the core. A gripping member 3I is shown pivoted on the pin 32 and provided with teeth which engage the strap end I I and force it against the flat surface of a flange 33 to prevent the strap end I I from moving to the left with respect to the head 22. An arm 34 is provided for raising the gripping member 3| from engagement with the steel strap end I I when it is desired to release it.

The head 2I is provided with a gripping member 35 which alsofipresses against the strap end I I, forcing it against the flat surface of the flange 36 for tightly gripping the strap end I I between the members 35 and 36. Upon operation of the tool I, the lever 26 is operated back and forth, such as between the positions shown in Figs. 1 and 3, and through a suitable ratchet mechanism operates a pinion engaging the rack 24 on the bar 23 to move the head 22 to the left or away from The end I I of the strap 6 is pulled through the clip 8 which engages the jaws 28 and 29 until the proper tension is applied to the strap 6.

During the operation of the lever 26 back and forth, for the purpose of operating the strapstretching tool I, force is communicated through the levers 26 and 25 and a pinion to the rack 24 for moving the head 22 to the left upon movement of the lever 25 to the right.v As best shown in Figs. 2 and 3, the lever 25 is mounted by a pivot 39 on thehead 2i and the lever 26 is mounted on the lever '25 by a pivot 4!. A rod or stud 42 is attached to the lever 26 by a pin 23 and extends through an opening 44 in the lever 25 through a washer 45 and carries a washer 46 and nut 4! on the outer end. A spring 48 is positioned between the washer 45 and washer 45 through which force is communicated from the lever 26 to the lever 25 upon movement of the lever 26 to the right, as illustrated in the drawings. As the tension on the strap end H increases, the force communicated through the spring 58 likewise increases, causing a certain movement of the lever 26 with respect to the lever 25 in order to effect a sufiicient compression of the spring 48 to apply the required force to the lever 25. As the force required to be transmitted through the spring 48 increases, the angular separation of the levers 25 and 26 likewise increases. Upon a predetermined angular separation between these two levers, corresponding to a predetermined force applied to the strap II, the lower end 49 of the pawl 50 that is mounted on a pivot in the lever 26 slips past the upper end 52 of the lever 25. This pawl 50 is continuously biased, by a spring '53 connected between the outer end of the pawl at 54 and the lever 26 at 55, so as to rotate in a clockwise direction, as shown in the drawings. When the pawl 50 is so released, a tooth 56 thereon is moved by the spring 53 to engage one of the teeth 51 carried by the ratchet 58 from the frame of the tool, thus preventing further operation of the lever 26 toward the left, as viewed in the drawings. A collapsible joint is provided at El in the lever 26, so that, upon a sufficient application of force to the handle 21, this joint will break to prevent further operation of the tool. the invention of this application, further details in the description thereof are deemed unnecessary.

The calibrating tool 62 of the invention is shown in Figs. 3 and 4 and comprises a calibrating sleeve 63 and a cylindrical member 64 for receiving the calibrating sleeve, the two members being shown as telescoping the one within the other. A slot 65 is shown along the length of the cylindrical member 64 in which slides guide and stop members 65 that are attached to the calibrating sleeve 63. A calibrating spring 6! is provided within the two cylindrical members 63 and 64 and engagesabutments 68 and 69 which close the opposite or outer ends of the two cylindrical members. The abutment 68 is formed-on a plate member II fastened by means of screws I2 in the outer end of the calibrating sleeve 53, and provided with a slotted spring guide portion 13 that is cylindrical in form' and extends within the spring 61 to prevent it from buckling. A slot I4 is provided lengthwise of the guide member I3 to accommodate a strap 75 that extends lengthwise through the member l3 and through a slot IS in the abutment member 59 at the outer end of the cylinder 64. A plate TI is provided to be attached as by screws I8 to the abutment member 69 for holding the bent end I9 of the steel strap 15 in the position illustrated in Fig. 4. V g

In order to calibrate the strap-stretching tool I, the proper size of band or steel strap 15 is passed through the slot I4 in the member II and the slot It in the abutment member 69 and bent upwardly, as shown at I9, and clamped in position by the plate 'I! to hold the strap firmly attached to the abutment member 69. The tool to be calibrated is then positioned, as shown in Fig. 3, so as to grip the outer end of the band I5, this band being held firmly between the holding members 35 and 36 of the tool. The tool is then operated in the usual manner by moving the lever 26 back and forth to increase the tension on the strap. This operation results in the movement of the heads 2I and 22 of the tool away from each other, thus forcing the calibrating sleeve 63 to the left with respect to the cylindrical member 54 against the compression of the calibrating spring 61. When this operation has been carried to the point where the locking mechanism of the tool operates, as above described, the compression of the spring as read on the calibrating member indicates the existing tension on the steel band I5. If this tension is above or below the desired tension at which the locking mechanism of the tool I shouldbperate, the tool may be adjusted accordingly, so that the locking mechanism will operate at the desired tension.

In order to readily disengage the bandingtool from the calibrating tool, a clamp 8!, shown in Fig, 6, is provided having a frame adapted to be positioned substantially about the calibrating tool 62 when the screw-threaded shaft 82 is withdrawn, and upon the operation of the'shaft 82 inwardly against the end of the calibrating tool, the members 63 and 64 are further telescoped so as to relieve the pressure against the jaws 28 and 29 of the strap-stretching tool, so that the gripping members 3I and 35 thereof may be readily disengaged from the strap I5. Upon subsequent movement of the member 82 to the left, as shown in Fig. 6, the calibrating tool I is positioned between the end 84 of the member Since the banding tool is not a part of 82 and the bifurcated end 85, 86 of the member 8| is released, allowing the calibrating spring 61 to expand until the telescoping members 63 and 64 are again in their extended position, as shown in Fig. 4.

Modifications of the structure described within the spirit of my invention will occur to those skilled in the art, and I do not wish to be limited otherwise than by the scope of the appended claims.

I claim as my invention:

1. The combination in a calibrating tool, of a pair of relatively movable, hollow cylindrical telescoping members each having an abutment member at its outer end, a calibrating spring within the pair of members for engaging the abutments in their outer ends, indicating means responsive to the relative movement of the cooperating hollow cylindrical members for in-. dicating the pressure applied b a strap-stretching tool being calibrated, each of said abutment members having a slot therein for permitting a steel strap to pass therethrough, a plate associated with one of said abutment members for clamping the end of the strap to the abutment member for holding it tightly in place, guide means for supporting the steel strap within the relatively movable cylindrical members and for permitting the strap to extend through the slot in the other one of the two abutment members, said calibrating tool being responsive to the operation of a strap-stretching tool operative to grip the band and to press the nose of the strapstretching tool against the free abutment member of the calibrating tool for forcing the relative movement of the two hollow cylindrical members against the force of the calibrating spring.

2. The combination in a calibrating tool for calibrating the force applied by a strap-stretching tool having a pair of relatively movable heads for applying an increasing pressure on a strap upon movement of the heads of the tool away from each other, the calibrating tool comprisin a pair of telescoping relatively movable tubular members having abutments at their opposite ends, a calibrating spring within the members and engaging the two abutments, a slotted spring guide member extending inwardly within the calibration spring from one of the abutments and having a slot extending lengthwise therethrough and through the associated abutment, a slot in the other of the two abutments at the other end of the tool, the two slots permitting a, steel strap to extend through the two abutments and the pair of relatively moving telescoping members, a plate removably attached to the outer surface of one of the two abutments and adapted for clamping the end of a steel band extending through the calibrating tool tightly to the abutment, the outer surface of the other abutment of the calibrating tool being adapted to receive the force from one of the two movable heads of the strapstretching tool being calibrated upon operation of the strap-stretching tool to apply pressure to the strap extending through the slot in the second-named abutment of the calibrating tool by relative movement of the two heads of the strapstretching tool to effect relative movement of the telescoping members of the calibrating tool and to compress the calibratin spring, and indicating means responsive to the relative movement of the telescoping members for indicating the pressure applied between the abutment members by the strap-stretching tool.

3. The combination in a calibrating tool, of a pair of relatively movable members each having an abutment portion at its outer end, a calibrating spring within the pair of cylindrical members for engaging the abutment portions of the relatively movable members, indicating means responsive to the relative movement of the cooperating relatively movable members for indicating the pressure applied by a strap-stretching tool being calibrated, each of said abutment portions havin a slot therein for permitting a steel strap to pass therethrough, a plate associated with the abutment portion of one of said relatively movable members for clamping the end of the strap to the abutment portion for holding it tightly in lace, guide means for supporting the steel strap and for permitting the strap to extend through the slots in the two abutment portions, said calibrating tool being responsive to the operation of a strap-stretching tool operative to grip the band and to press against one abutment portion of the calibrating tool for forcing the relative movement of the two relatively movable members against the force of the calibrating spring,

4. The combination in a calibratin tool for calibrating the force applied by a strap-stretching tool having a pair of relatively movable heads for applying an increasing pressure on a strap upon movement of the heads of the strapstretching tool away from each other, the calibrating tool comprising a pair of relatively movable abutments, a calibrating spring positioned between and engaging the two abutments, a spring guide member extending within the calibration spring from one of the abutments and having a slot extending lengthwise therethrough and through the associated abutment, a slot in the other of the two abutments at the other end of the tool, the two slots p rmitting a steel strap to exend through the pair of relatively movable abutments, a plate removably attached to the outer surface of one of the two abutments and adapted for clamping the end of a steel band extending through the two abutment of the calibrating tool tightly to the abutment, the outer surface of the other abutment of the calibrating tool being adapted to receiving the force from one of the two movable heads of the strapstretching tool being calibrated upon operation of the strap-stretching tool to apply pressure to the strap extending through the slot in the second-named abutment of the calibratin tool by relative movement of the two. heads of the strapstretching tool to effect relative movement of the abutments of the calibrating tool and to compress the calibrating spring, and indicatin means responsive to the relative movement of the abutment members for indicating the pressure applied between the abutment members by the strapstretching tool.

NICK MARS. 

